RCW : It isnt for the majority of laymen to decide that something is true simply because it seems to make sense,Id leave that to to the AES guys. But yes a BP4 does seem to approximate the horn below Fc. Have you seen the distortion measurements vs frequency here->http://homepages.paradise.net.nz/sbk1/ssi.htm

Re DB keele,yes its true but if you cant afford multiple 18"s with appropriate EQ isntead of your single HT woofer on a massive horn its no use. (bearing in mind that we are talking HT not midbass)

You could just chuck the largest flare extender you can fit onto a labhorn size unit - FR can be worked out with hornresp.(single 18"/ 2 x 12"s or similar)
For HT I wouldnt have a cutoff any higher than 25hz or so. I wouldnt be expecting 16hz horn loaded.

I would expect no other reaction than that from someone who describes such observations as "bollocks" Brett, and then goes on to describe the sound of his horns in subjectivist aesthetic terms.
Perhaps in your case it is some sort of British understated aesthetic.

Small size and low frequency output together cannot be accomplished with a horn. THat's a statement we all have to agree is true.

The statements about output below Fs are convienient for the point at which they are measured. That is below Fs. Above Fs a horn will produce more volume with less power input than any other box configuration period. That is part of the allure!

The other part is it's dynamic range. Granted a huge bank of Vented sub monkey coffins can be coaxed into submission with enough kilowatts to become dynamic. I have both done it and heard it. Frightening! But the volume of the boxes and the cost of the rig driving them is not negligable.

But a smaller complement of drivers with power orders of magnitude lower will outperform the monkey coffins if they are coupled to a horn. ( horse coffin ) ( have to be fair to monkeys ) The trade off is the size. The design limited bandwidth to is a definite tradeoff. ( allthough there are definite design limits to reflex designs to ) But the realistic punch and apparent limitless power is very alluring.

As someone who spent a good many years playing in the back row of an orchestra. I say that hands down a horn portrays the reproduced sound with the greater realism.

> Small size and low frequency output together cannot be accomplished with a horn.
Well, it depends...
Lets take an infinite, open-air acoustical environment.
We have a cone, and we want to radiate sine soundwaves.
(The cone now just radiate in one direction for simplicity)
At a given frequency the efficiency of sound radiation depends
on the size of the cone. For a lower frequency a bigger cone
is ideal, cause a low freq sound means slow air-movements, and
therefore a lot of time to the air to escape far from the cone
in every direction. Therefore air will rather just move instead
of compression and pressure-variation (generating sound).
Increasing the frequency the radiation is getting even more directed,
cause for the air particulars its easier to radiate the sound in the
cone's axle, instead to propagate it all around the cone.
Now then, its clear that for great bass we need a cone as huge as possible.
But (and thats the point) in a closed place this work a bit different.
In this case we need more power to radiate, cause we must compress the air
in this place a bit. (The walls and the corners push back the waves...)
So there is an important thing, that peoples often forget:
Where do we want to achieve the bass improvements with our horn ?
Remark, that a BR enclosure can also help a lot in bass reproduction,
although it has just a little port. Now then, the are two extremity of
sound radiating:
- small area & big amplitude
- huge area & tiny amplitude
A panel-loudspeaker is rather the second type and a dynamic
speaker with coil and magnet is rather the first type.
With an average subwoofer speaker we have a finite power, and the speaker
alone can radiate low freqs with just a small efficiency.
Now with a horn we can make a transform between the two extremity above.
And we should do this too, cause in a closed air-space there is an optimum
horn-sizing for a given speaker. Not the horn with the biggest mouth is
definitely the optimum.

Again I ask, what is the consensus regarding a large chambered rear horn in order to achieve true subwoofer extension in a relatively compact horn size? It seems to work well in cabs like the Jensen Imperial.

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Why is it that I always hear RCW saying that a horn approximates a 4th order bandpass below the cutoff. What does a 4th order bandpass approximate below it's cutoff? A SEALED BOX!!!! why cant you just say a horn approximates a SEALED BOX below its cutoff!!!!

That's below the horn cutoff. The band pass cutoff can be much lower. This is also my point regarding using large chambered horns. For a sub all we need is a narrow bandwidth, eg 20hz to 80hz is just 2 octaves. If the lower end is really ported output with some loading, who cares as long as you get the extension.

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why dont we use rear chambered back horns? well for one I dont have any clue how to design a good one, for two, it's still huge, and well maybe it still has the same bass reflex sound to it, i dont know. I've never heard one....